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The present invention relates, in general, to a double metal cyanide complex catalyst for producing polyol used in producing polyurethane and, in particular, to a double metal cyanide complex catalyst useful for producing polyoxyether polyol and polyether polyol.
A double metal cyanide complex catalyst for producing polyol is generally expressed by formula I, below:
Ma[Mxe2x80x2(CN)6]bLcxe2x80x83xe2x80x83Formula I 
wherein, M and Mxe2x80x2 are metal elements, L is a complexing agent, and a+b+c+d equals a sum of electrovalences of M and Mxe2x80x2 and a, b, c, and d are integers.
The present invention provides a double metal cyanide complex catalyst for producing polyol expressed by formula I, which is produced by using a monovalent alcohol such as ethanol or butanol, and polyvalent alcohol such as polypropylene glycol as the complexing agent.
Polyol is a compound with plural hydroxyl groups, and polyurethane is produced by the condensation reaction of an isocyanate compound with polyol.
Polyol used in producing polyurethane is produced by the epoxide polymerization reaction of hydrocarbon-based oxide such as ethylene oxide or propylene oxide, with the use of a polymerization initiator in the presence of an alkali hydroxide catalyst such as KOH.
The epoxide polymerization reaction is a reaction which produces polymer by a ring-opening reaction of epoxy group, as expressed by the following formula. 
Characterized by urethane bonds (xe2x80x94NHxe2x80x94COxe2x80x94Oxe2x80x94), polyurethanes are versatile in size and kind as exemplified by those used in construction, fibers, foams, elastic bodies, and pigments. A flexible urethane is produced by using polyol with the relatively high molecular weight of 3000 to 6000, and a rigid urethane is produced by using polyol with a low molecular weight of 150 to 1000.
The double metal cyanide complex is produced by reacting metal salts and metal cyanide salts with the complexing agent.
Metal salts are expressed by M(X)n, where M is the metal element and X is a compound constituting salts. Examples of metals used in producing the double metal complex include Zn (II), Fe (II), Ni (II), Mn (II), Co (II), Sn (II), Pb (II), Fe (III), Mo (IV), Mo (VI), Al (II), V (V), V (IV), Sr (II), W (IV), W (VI), Cu (II), and Cr (III), and the compound constituting salts are exemplified by halogenate, hydroxide, sulfate, carbonate, cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate, carboxylate, and nitrate. Typically, n is an integer of 1 to 3, depending on the valence of the metal.
Metal salts used in producing the double metal complex include zinc chloride, zinc bromide, zinc acetate, zinc acetonylacetonate, zinc benzoate, zinc nitrate, iron bromide (II), cobalt chloride (II), cobalt thiocyanate (II), nickel formate (II), and nickel nitrate (II).
Metal cyanide salts may be expressed by (Y)aMxe2x80x2(CN)b(A)c, wherein Y is alkali metal or alkaline metal; Mxe2x80x2 is the metal element and is selected from the group consisting of Fe (II), Fe (III), Co (II), Co (III), Cr (II), Cr (III), Mn (II), Mn (III), Ir (III), Ni (II), Rh (III), Ru (II), V (V), and V (IV); A is an ion selected from the group consisting of halogenate, hydroxide, sulfate, carbonate, cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate, carboxylate, and nitrate; a and b are integers greater than 1, respectively; and the sum of electric charges of a, b, and c balances with the electric charge of Mxe2x80x2. Generally, an example of metal cyanide salts includes potassium hexacyanocobaltate (III), potassium hexacyanoferrate (II), potassium hexacyanoferrate (III), calcium hexacyanocobaltate (II), and lithium hexacyanoferrate (II).
Useful as the complexing agent is ethylene glycol, dimethyl ether, alcohol aldehyde ketone, ether, ester, amide, urea, or nitrile.
A double metal cyanide catalyst has been already suggested, which was prepared by using ethylene glycol or dimethyl ether as the complexing agent (U.S. Pat. Nos. 4,477,589, 3,821,505, and 5,158,922); and a catalyst prepared by using alcohol, aldehyde, ketone, ether, ester, amide, urea, or nitrile as the complexing agent (U.S. Pat. No. 5,158,992), as well as a catalyst prepared by using t-butyl alcohol (U.S. Pat. No. 5,780,584), have also been suggested.
However, catalysts prepared by using only one of the complexing agents as described in the above prior art have problems in that reactivities of the catalysts are low because the time required to activate them is too long, e.g. 4 hours or longer during epoxide polymerization, and unsaturation is high, up to 0.02 to 0.07 meq/g in the case of producing polyol with a high molecular weight of 3000 to 6000.
On the whole, a polyol is reacted with a diisocyanate to form a polyurethane in which urethane bonds are three-dimensionally arranged. But, unsaturated polyol negatively affects the polymerization of urethane.
Therefore, it is an object of the present invention to provide a double metal cyanide complex catalyst for producing polyol, which serves to reduce production of unsaturated polyol and shorten catalyst activation time, as well as resulting in not having to remove remaining catalysts from polyol after polymerization when polyoxyetherpolyol and polyetherpolyol are produced by an epoxide polymerization reaction.